DNA Is Solving Dozens of Cold Cases. Sometimes It’s Too Late for Justice.

Detectives in Yellowstone County, Mont., have never forgotten the 1973 murders of Linda and Clifford Bernhardt.

The young couple were found in pools of blood in their house in Billings. Both had been strangled, and Linda had been sexually assaulted. For four decades, investigators built a case file of more than 3,600 pages in the hopes that one day, they could announce that the killer had been found and would face justice.

Last week, with the help of DNA technology, that day came, but only one of those hopes was fulfilled. Investigators in Billings said they had finally identified a suspect — Cecil S. Caldwell — but there would be no justice. Unlike the 24-year-old victims, Mr. Caldwell lived a full life. He died in 2003 at age 59.

“Today is a good day, a somber day,” Attorney General Tim Fox of Montana said at a news conference on March 25 as he described the break in the Bernhardt case.

Beside him on a table was an array of thick case files that investigators had accrued over the years. “Even though at the time, the technology had not advanced to a point where someone might be identified, they knew and understood the importance down the road that everything they collected could eventually be important,” Mr. Fox said.

The increasing use of DNA and genetic genealogy has given new momentum to solving cold cases in the United States, from the arrest of the Golden State Killer suspect, Joseph James DeAngelo, 73, in California last year to the announcement in Alabama last month that Coley McCraney, 45, had been charged with raping and murdering two teenagers.

With such arrests, questions that have vexed investigators and haunted families for decades seem closer to being resolved. Suspects suddenly have a public face, peering out of mug shots. Some appear in handcuffs in courtrooms, making it possible there could be an understanding of the seemingly unanswerable question — why did they do it?

But for some families the technology comes too late. Unlike in the DeAngelo and McCraney cases, there wouldn’t be the satisfaction of an arrest for the families of Clifford and Linda Bernhardt.

“The human part in all of us wants justice,” Kelly Reich, Linda’s only surviving sibling, said in an interview after she found out that the suspect in her sister’s murder was dead.

“It is not closure,” she said. “Closure is when the door is shut and you can move forward and say everything is behind you.”

For those who have spent decades absorbing a family member’s violent death, the sudden discovery of a deceased suspect can recast a long period of yearning for justice. The Bernhardt couple’s remaining family members said in a statement that they were relieved by a “degree” of closure, but needed time to process the information.

“When I thought about it, it doesn’t matter,” Ms. Reich said later in the interview. “It doesn’t change the outcome.”

As in the other high-profile cold cases, investigators in the Billings murders used GEDmatch, an online genealogy database that traces distant relatives, with DNA samples submitted to Parabon NanoLabs, a forensic consulting company in Virginia that specializes in genetic genealogy.

Parabon said on Monday that since last May, the company has identified 47 suspects in cold cases. Nine of them, including Mr. Caldwell in the Billings case, were dead, never to face justice for crimes committed in states including Texas, California, Florida, Arkansas, Oregon and Maryland.

One of them was Kenneth Earl Day, whom investigators in Montgomery County, Md., named last month as a suspect in the rape of a 52-year-old woman in 1989, and in the rape and murder of another woman, Le Bich-Thuy, 42, in 1994. But Mr. Day, a carpenter, had died in 2017 at age 52, they said.

“I think it was relief,” Sgt. Chris Homrock, an investigator with the Montgomery County Police Department’s cold case section, said in an interview on Monday, describing how the daughter of the 52-year-old woman, who has since died, had been partly relieved that a suspect was found. “But she was sad her mom passed away without knowing who did this to her,” he said.

Relatives of the woman believed to have been killed by Mr. Day could not be found, Sergeant Homrock said.

“There are so many unanswered questions,” he said. “We are never going to know now.”

In the Billings case, Ms. Reich described a long process of coming to grips with her sister’s violent end, which she learned about as a 16-year-old high school sophomore. After the murders, her family, which included two brothers, scattered to different cities and states where no one knew about them. “Our lives were shattered,” she said.

Ms. Reich, now 61, said she and her family had been hoping for justice as detectives worked on the case. There were no DNA matches within a national criminal justice database, Sheriff Mike Linder of Yellowstone County said in an interview. The county cold case unit’s work with the genealogy technology last year eventually led to Mr. Caldwell, who had no previous criminal record.

“He was not really on the radar,” Sheriff Linder said.

But with the suspect dead, he and the team were unable to answer remaining questions. Why were pairs of Ms. Bernhardt’s underwear missing? What was Mr. Caldwell’s motive? As a former grocery warehouse colleague of Ms. Bernhardt, had he been infatuated with her?

Why had Mr. Caldwell signed the condolence books at his victims’ funerals?

Sheriff Linder said that when Mr. Caldwell’s family was informed that he was the suspect, there was “maybe some disbelief, maybe some not too surprised.”

The Bernhardts were childhood sweethearts and had been married a few years before they were killed. An obituary of Mr. Caldwell in The Billings Gazette, by contrast, describes a full life.

He had been married with two adopted children at the time of the Bernhardt killings in 1973, according to the obituary. He and his wife divorced five years after the murders. He remarried in 1979, and become a stepfather to the children of his second wife, Nancy. He had been working for the city and for a mail contractor when he died in 2003, it said.

“He was loved by all and will be greatly missed,” it said.

Nancy Caldwell died in 2014. Her and Mr. Caldwell’s ashes were scattered in the ocean surrounding Maui, “a place they loved so much,” her obituary said.

Ms. Reich said she imagined Mr. Caldwell looked over his shoulder now and again.

“Maybe every day he woke up wondering if there was going to be a knock on the door,” she said. “For right now, it is too much to process. It is just enough to process the fact that after 45 years, we have a face and a person.”